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I was wondering if any of you clamp with a vacuum. As I understand it it takes very little vacuum to hold something down but I could be wrong. I am talking about clamping small things like less than a foot square. This may not be worth the effort, I don't know.
 

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I was wondering if any of you clamp with a vacuum. As I understand it it takes very little vacuum to hold something down but I could be wrong. I am talking about clamping small things like less than a foot square. This may not be worth the effort, I don't know.
@ hawkeye.Hi Don,I don't know the answer to your question but it is a very good question.Anyone with imagination can see a work area,connected to a vacuum system hooked up to fences or tables,jigs,feather boards & the like where, rather than turning knobs,nuts,screws & other adjustments,one could simply attach a small hose with a pre-set vacuum,& your ready to go. Of course I am over-simplifying this,it's what I'm good at.lol.If this is done already,I swear I didn't know.Jamesjj777746.
 

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About 10 + years ago there was a company booth at "The Woodworking Shows" that sold a bunch of vacuum attachments and hold downs. I didn't buy from them at the show, but tried about a year later and they were out of business. They made round and square vacuum chucks with O rings top and bottom and push connect fittings in the edge for connecting 1/4" OD poly tubing, They also made a circle cutting adapter that did not require a center pivot hole to be drilled. It was held in place by vacuum. Their products were mostly made from aluminum.

I have since thought of making similar vacuum fittings using 3/4 Baltic Birch and grooving it for O rings, then drilling the needed ports and installing push connect fittings. It wouldn't be hard. I just never seemed to need them bad enough to do it. There is now a closed cell Weatherstrip type tape that they sell for CNC work that might make the construction easier, because O rings and the needed grooves for them wouldn't be required.

If you do it, I want to see pictures.

Their standard vacuum chuck was just a round slab of 3-4" diameter aluminum about the size of a hockey puck, but 5/8 or 3/4 thick. It had a hole completely drilled through the center and another intersecting hole completely drilled from one edge to the opposite side. These second holes had push connect fittings in them that allowed them to be connected together and to the vacuum source. An O ring groove and O ring almost as large as the top and bottom face formed the vacuum seal Several of these could be connected together. Then with a plug in one port of the last one, and a vacuum line connected to the first one, vacuum would hold the part in place as well as hold all of these vacuum chucks to the work bench. They also had one sided versions of these with threaded screw holes in the bottom for attaching to a fixture or bench. Their circle attachment just had one O ring on the bottom and the top had a pivot connection in the center for a router circle cutting attachment. Only one vacuum fitting was in the edge, since I guess they didn't expect this to be used along with the hold downs, but it probably could be if attached to the end of the string.

Charley
 

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Right! The vacuum chuck eliminates the need for clamps. Remove the air under the piece to be clamped, and atmospheric pressure holds the part in place, usually with more force than most clamps can apply. Many production CNC machines use vacuum hold downs. Many of these hold downs are designed to be easily re-configured so the program doesn't cut through one of them. Production CNC machines is where you will find them mostly used.

For work bench use, I think they could be quite handy if they could be easily re-configured, which is why I was impressed with the products being offered in that woodworking show booth. Their holding power is way better than a router mat and increases as the area of vacuum is increased. A holding force 14.7 lbs per square inch if the vacuum level is good, so a small 3" X 3" vacuum chuck would have 132 lbs of force holding the part if the vacuum level was good.

OK, I'm re-inspired to make some of these. I think I have everything that I need, except maybe the time. I'll let you all know what I end up with.

Charley
 

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Discussion Starter #7
I was think about clamping for routing operations. I saw this in a Patrice Spielman book that was dated 1988. They said it took very little vacuum like about as much as a vacuum that is created sucking through a straw. They also said vacuum motor from a refrigerator do it. I saw where Harbor Fright had on for $18. You would also need a few fittings and tubing.
 

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Don, You must first determine that the vacuum is the bypass type motor. which uses air intake separate from vacuum air to cool the motor. A non bypass vacuum uses exhaust air from the vacuum to cool the motor and if you seal off incoming air from the vacuum hose you would overheat the motor. A non bypass vacuum motor could conceivably turn into a fire starter by intaking flameables and passing that air past sparking brushes as it cools the motor. Just my 2 cents.
 

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I worked in a cabinet factory for a short time and the CNC router used vacuum holdown. It seems to me I had to configure it to fit what was being run. I didn't spend much time on it. Most of my time was on a CNC beam saw. I loved running that machine.
 

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I have a CNC router. I use a modular system that I designed myself, with great success. I use a vacuum pump for my system but a shop vac can provide more than enough holding power even if you used a plywood plate and Frost King foam gasket with the self stick tape for your general use. Good luck with your project.
 

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Discussion Starter #12
I have a CNC router. I use a modular system that I designed myself, with great success. I use a vacuum pump for my system but a shop vac can provide more than enough holding power even if you used a plywood plate and Frost King foam gasket with the self stick tape for your general use. Good luck with your project.
Jim could you go into more detail on how you made your vacuum clamp. I think it would help several wood workers on this forum.

Thanks Don
 

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OK, I promised to build a vacuum chuck so you could see what it takes. The ones that I've seen were made from aluminum, but Baltic Birch will work as well. The ones that I made were made from Birch plywood scraps (not Baltic Birch) so I hit a void while making them and had to fill it to prevent a leak. I had this piece of scrap and didn't happen to have 3/4 Baltic Birch handy, so just went with what I had. You will be much better off using real Baltic Birch for this.

Attached are two photos of one of the ones that I made today. This one has an O-Ring almost 4" in diameter, because I happened to have a few fat O-Rings on hand that size. Smaller, like 3" diameter fat O-Rings should make good smaller vacuum chucks just as good for routing work. So I cut the 3/4 birch plywood 6" square to fit my O-Ring size, and then drilled a 1/4" hole in the center. For a single sided chuck, drill this hole about 1/2" deep. For a double sided chuck, drill the hole all the way through.

I used my DeWalt DWP611 plunge router together with my CRB7 jig and a 1/4" down spiral bit to make the O-Ring circle grooves. Most any small router and a good adjustable circle jig can be used. The dimensions of this groove are somewhat critical and will require experimenting, based on the particular O-Rings that you end up using. If you buy O-Rings, there are prints available containing the needed dimensions, or a cross reference table to show the dimensions of every O-Ring part number. I didn't have a part number for my O-Rings, so I just cut a few grooves until I got the dimensions right. A groove that's too wide is OK, as long as the O-ring fits tightly around the plywood center of the groove, but not so tight that it won't stay in place, and the O-Ring sits slightly above the surface of the plywood when it's fully bottomed out in the groove. (see pictures).

A cross hole needs to be drilled in the exact center of one edge to intersect with the previously drilled center hole. Only drill in from one side if you will NOT be connecting another vacuum chuck to this one, or drill two holes from opposite sides if you will be connecting another vacuum chuck to this one.. This hole diameter should be about 3/16 and must be drilled accurately and straight so it doesn't break through into the O-Ring grooves. The ends of these holes then need to be drilled larger to allow threading the 1/8" pipe thread fittings into them. Again, be careful not to drill any deeper than necessary to keep from breaking into the O-Ring grooves. If these holes are too loose a little epoxy will hold the fittings in place.

I drilled screw holes in the diagonal opposite corners, so I could mount the chuck shown to my work bench. If you made O-Ring grooves on both sides and drilled the center hole all the way through, vacuum will hold the chuck down to your smooth work bench surface as well as holding your part to the top side of the chuck.

My experiments with this quickly made chuck have been very satisfactory and have inspired me to make more of them, but take the time to make them as perfect as I can. It works so good that I think I could have picked up one end of my work bench by pulling up on the test piece if I had tried hard enough. My vacuum pump is an old refrigeration service compressor. It doesn't have much flow, but it can develop 29+" of vacuum quickly with this chuck, if there are no leaks. I highly recommend installing a filter trap in the line going to the vacuum pump, to keep dirt and sawdust from going into the vacuum pump. In use the part to be clamped against the O-Ring. Air is drawn out of the space between the part being clamped and the plywood chuck space inside the O-Ring through the center hole and then out through the side hole and fitting and into the vacuum pump. This will actually pull the part being clamped down hard against the plywood vacuum chuck because of the lack of air pressure inside the O-Ring and the 14.7 pounds per square inch of atmospheric pressure on the top of the part being clamped. So the force is pi X Radius squared X 14.7 pounds per square inch, or roughly 175 pounds of force for this 4" vacuum chuck (if I rough calculated the math right).

The fittings that I happened to have in my shop accept 1/4" OD plastic tubing, which must be cut cleanly and squarely with a razor blade for them to seal inside the fittings properly. The little red plastic collar on the end of the fitting releases the tubing from the fitting when you push it in while pulling out on the tubing, so it's easy to assemble and dis-assemble over an over again when working with it.. The fittings don't have to be brass for this use, but they are what I happened to have available. There are similarly designed plastic fittings that will work just fine for this and they are much cheaper.

Automation Direct www.automationdirect.com near Atlanta, GA sells this tubing and the fittings for it quite reasonably, but they are also available from Grainger, McMaster Supply, etc. at higher prices. I buy the 1/4" OD plastic tubing and the mating 1/8" pipe thread fittings for use in pneumatic controls for automated machinery that I frequently work on, so I always have some of this hardware in my shop. It's suitable for both air and vacuum and comes in many sizes, but 1/4" works well for these vacuum chucks.

There is a closed cell foam kind-of Weatherstrip with a sticky backing that many CNC users use for their vacuum chucks. I haven't done any searching for it yet, but it would make it much easier to make vacuum chucks, since an O-Ring groove and O-Ring would not be necessary. Just stick this closed cell foam on the board in any shape and area as long as both ends of the foam meet and a vacuum port is located somewhere within that rough circle. I guess I'll be searching for a source of some of that foam tape. I'll let you all know the source when I find it.

Charley
 

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My system is the same that Charley just displayed. Only difference, I use 1" thick HDPE (high density polyethylene) for the suction plate. I make a few products using the HDPE and keep it in stock from 1/2" thickness to 1" so it makes a nice plate. I also used the same 1/4" plastic airline and fittings.

I use mine with the CNC router. As for the gasket I buy the 1/4" cord type foam rubber from MSC in 100' rolls. They recommend the special adhesive to join the gasket together but I use crazy glue from Locktite with no adverse problems.

For the vacuum pump I have an old oil filled pump that was used for evacuating air conditioning systems and a small oil filled unit that I purchased from Harbor Freight when they had a nice sale. (Only buy from HF when they publish sale prices on item I want)
 

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Discussion Starter #16
Charley and Jim thanks for the great work y'all have done help me with this. It looks to me that this clamp could make life easier for a lot of wood workers.
 

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I agree. I wish I had taken the time to make these much sooner. With that one single sided chuck in the pictures screwed down to the bench, I can vacuum clamp anything that has a smooth bottom surface large enough for the chuck to grip to, and once the vacuum pump is turned on, that piece isn't going anywhere. The vacuum is enough to pull the piece down flat against the top surface of the chuck and there's no way it's going to move while working on it. My force calculation in my previous post says it should betterthan getting my 150 lb plus wife to stand on it while I route.

Now I've got to get some closed cell foam Weatherstrip to try making chucks of different shapes easier. The O-Rings work well, but cutting the groove "just right" can be tricky. The groove wouldn't be necessary at all with the foam Weatherstrip, although it might wear out quicker.

Don, thanks for moving this up to the top of my priority list. Making these has been on my list for years. I should have made them over 10 years ago.

Jim, I like your HDPE version, but in a non-production shop I think it's a bit costly. I question whether the foam
Weatherstrip will stick well to HDPE too, although many other plastics, and I know that aluminum will work just fine. I'll learn more after I get some of that Weatherstripping tape.

Charley
 

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Discussion Starter #18
I agree. I wish I had taken the time to make these much sooner. With that one single sided chuck in the pictures screwed down to the bench, I can vacuum clamp anything that has a smooth bottom surface large enough for the chuck to grip to, and once the vacuum pump is turned on, that piece isn't going anywhere. The vacuum is enough to pull the piece down flat against the top surface of the chuck and there's no way it's going to move while working on it.

Now I've got to get some closed cell foam Weatherstrip to allow making chucks of different shapes easier. The O-Rings work well, but cutting the groove "just right" can be tricky. The groove wouldn't be necessary at all with the foam Weatherstrip, although it might wear out quicker.

Don, thanks for moving this up my priority list. Making these has been on my list for years. I should have made them over 10 years ago.

Charley
Charley what are you using to create the vacuum and how is it hooked up. You seem to have done this quickly.
 

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Jim, I like your HDPE version, but in a non-production shop I think it's a bit costly. I question whether the foam
Weatherstrip will stick well to HDPE too, although many other plastics, and I know that aluminum will work just fine. I'll learn more after I get some of that Weatherstripping tape.

Charley
Yes you are right about the expense of HDPE. But since I have it, I make use of it. I have used Corian and wood as well. My gasket material is 1/4" diameter. There is no adhesive to hold it in place. I use a 1/4" round nose (core box) bit at .150" depth. This allows for the part to be cut to sit flat on what you refer to as the chuck. it also makes it easier to replace should it get damaged. I tried the foam tape with adhesive and found that the work piece sometimes doesn't pull down flat to the chuck. This can reduce the amount of contact surface that helps hold the cut part in place. If you noticed in my pics, you can see that I cut vacuum tracks out from the supply hole to increase the flow of vacuum/suction.

The accuracy of the cut depends on what your project part is and what it will be used for. For what I am doing I need to maintain a tight tolerance but for the non business application this may not be necessary.

One thing that I have also done is to apply the gasket material to both sides of the chuck plate. When the vacuum is applied it pulls to the table as well as the part you are trying to hold down, eliminating the need to screw the chuck down. This may be helpful for you or any of the forum members that want to use this type of hold down system.

Good luck to all that want to experiment with this system.
 

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Discussion Starter #20
Charley and Jim y'all have done a lot of work on helping me and others understand this.

Thanks

PS- I still don't don't understand about using a vacuum pump or an air compressor and how it's done. I have a 30 gallon air compressor and air brush air compressor.
 
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